Biological Molecules - Lipids

Question 1

What do all Lipids contain?

Answer 1

Hydrocarbons

Question 2

What are the 2 groups of lipids?

Answer 2

1. Triglycerides

2. Phospholipids

Question 3

How are Triglycerides formed?

Answer 3

Condensation of one molecule of glycerol and three molecules of fatty acid

Question 4

Describe one feature of Fatty Acids and explain how it aids its function.

Answer 4

The tails are hydrophobic, making lipids insoluble in water

Question 5

Draw out the structure of a Triglyceride.

Answer 5

Refer to textbook.

Question 6

Draw out the structure of a Fatty Acid

Answer 6

Refer to textbook.

Question 7

What are the 2 types of Fatty Acids?

Answer 7

1. Saturated

2. Unsaturated

Question 8

`What type of fatty acid doesn’t have any double bonds between their carbon atoms?

Answer 8

Saturated

Question 9

What type of fatty acid has double bonds between their carbon atoms?

Answer 9

Unsaturated

Question 10

What bond is formed between glycerol and a fatty acid?

Answer 10

Ester Bond

Question 11

How many times does a condensation reaction between glycerol and a fatty acid happen to form a triglyceride?

Answer 11

3

Question 12

What lipids are found in cell membranes?

Answer 12

Phospholipids

Question 13

What is the difference between a Phospholipid and a Triglyceride?

Answer 13

In a phospholipid, one of the fatty acid molecules is replaced by a phosphate-containing group

Question 14

Describe 3 features of Triglycerides and explain how it aids its function.

Answer 14

1. Triglycerides are mainly used as energy storage molecules. They’re good for this because the long hydrocarbon tails of the fatty acids, contain lots of chemical energy
2. They’re insoluble in water, so they don’t affect the water potential of the cell and cause water to enter the cell by osmosis, which would cause the cell to swell
3. The triglycerides bundle together as insoluble droplets in cells because the fatty acid tails are hydrophobic

Question 15

Describe one feature of Phospholipids and explain how it aids its function.

Answer 15

Phospholipid heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side. The centre of the bilayer is hydrophobic, so water-soluble substances can’t easily pass through it - the membrane acts as a barrier to those substances

Question 16

Describe the Emulsion Test for Lipids.

Answer 16

1. Shake the test substance with Ethanol for about 1 minute
2. Pour the solution into water
3. +ve= Milky emulsion